This invention relates to collapsible steering wheel columns of the resettable type for motor vehicles.
Pertinent prior art includes the following U.S. Patents: Fergle U.S. Pat. No. 3,487,710; Weiss, U.S. Pat. No. 3,540,304; Olsen U.S. Pat. No. 3,678,777 and Hollins U.S. Pat. No. 3,798,994.
In accordance with one prior art device, it is proposed that one of the shafts of a steering column on a motor vehicle either telescope outwardly or collapse inwardly by the activation of an explosive charge during the initial stages of a serious crash or accident. In a sub-critical crash, the force would be insufficient to activate the explosive charge but the shafts would still telescope one into the other to absorb the energy from the impact force of operator movement into the steering wheel. Obviously, this arrangement is very complex and requires replacement parts after each crash before the steering wheel column can be used again. Although this construction might be suitable for some automobile applications, it is hardly applicable for construction equipment which often requires the vehicle to be put back into operation shortly after the accident or crash.
Still other proposals include the provisions of tubular members between the steering wheel and the support brackets of the column. Such members are designed to absorb energy by controlled deformation of the member when an impact load is exerted against the steering wheel. Besides various other limitations, these steering wheel columns are not resettable without new parts after an accident.
Another proposal employs a padded cushion between the steering wheel and the instrument panel of the vehicle. The steering wheel column is comprised of telescoping members that are held in a fixed operating position by gripping spring fingers until the fingers are forced out of their respective indentations by the operator being thrust against the steering wheel which results in the steering wheel collapsing toward the padded cushion. The cushion is expected to absorb the energy from the impact and to protect the driver from injury. In practice, however, the fingers of an operator could easily be pinched between the steering wheel and the cushion in a crash. Moreover, because there is a rigid support member beneath the cushion which limits the energy absorption abilities of the cushion, there may be inadequate absorption of the impact force in case of a serious crash.